gardner



Jan. 10, 1928.

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Filed May 25. 1921 2 sheets-sheet 1 Inuan nr J ch11 ElQsrzfner Jan. 10, 1928. 1,655,602

J. E. GARDNER AUTOMATIC rrausnows SYSTEM Filed May 25, 1921 2 Sheets-Sheet 2 -Inusn czr John EEardhar changes, and which are well flrn Patented den. 1%, i928,

master JOHN E. GARDNER, OF CI-LICAGG, ILLINOIS,

ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATZC nnncrnro Inc, or GHICAGQ, ninrnors, A CORIORATION or DELA- HARE.

Application filed May 25,

The present invention relates in general to automatic telephone systems, but is more especially concerned with systems of the type. which are installed in small automatic e1;- own connnercially as private automatic exchanges. in such systems it is usual to provide certa n special features which are unnecessary in larger exchanges, among which is an arrangeinent known as discriminating service. According to this ieature the suhscrihers in the exchange are divided into groups or classes, thenuinber ot these hei 'deper 1 upon the number of classes Oif SGIVlC necessary to give, and the subscribers entitled to the various classes of serviccare put in their respective groups.

Gne ot' the objects of the present invent on is to provide a new and iin roved discrnn inating service arrangement in a private autoniatic exchange, wherein an operator is employed to extend all connections outgoing froin the exchange to other exchanges. In

the present case the subscribers are divided into four Olaf-35598 in accordance with the dif fcrcnt clue es of service to which they are entitled and means are provided for notitying the operator whenever an outgoing call is niade just w rat other rchanges the calli subscriber is entitled to be connected 'with. y

A second object of the invention is to provide a novel and improved type of rotary line s *itch which is individual to a subscribers line.

A further object of the invention relates to the provision oi a. new and 'in'iprovcd circuit whereby a selector switch may a directively controlled movement on cer levels, this being necessary in ca? necessary to call any one o;

the operators. There are other objects of the invention not now specifically mentioned which together with the foregoing, will he described hereinafter, reference be ng had to the accoinpanying drawing in which Fig. 1 shows an automatic substation A, the individual line switch C, and the selector E, while 2 shows incoming trunk l ne terminating in-jaclr J as the attend operators switchboard, a cord circuit 9, and portions of two out oing ,truul'; rating in jaolrs being shown in the drawin 's.

aUroMA'r-ro rnrinrrronn sysrniu.

1921. Serial No. 472,536. I

J and J over which calls may be extended to other exchanges.

Referring now to the drawings, in Fig. 1 is shown an automatic substation A or the usual type, the associated line of which terminates in the exchange in an individual line or trunkselecting switch C. This line switch is of the usual rotary type whose wipers have no normal position and whose function it is to extend the associated line, when calling, to an idle :lir'ct selector switch such as the one shown at E. The circuits of the line switchC are somewhat difierent from those usually employed in accordance with the present invention and will be described fully hereinafter.

The selector E to which the line switch C in common with a plurality-of other line switches have access is of the usual Strowger vertical and rotary type, the circuits of which have been designed to operate in the improved system. These first selectors, such as E, have access troni the first nine levels of their bank contacts to local connector switches ot the usual Strowger type. These connector switches have not been shown in the drawings, but have the usual functions and are the last in a series of switches used inextending connections to local called lines. ()n the tenth level the selector E has access to trunk lines leading to operators position-s, one of these being shown in the drawings comprising .conductors 140-142, inclusive, and terminating at an ogerators position in jack J, Fig. 2.

alls coming in over the trunk line terminating in jack J are adapted to be extended by the operator through the medium of cord circuit such as-O, or similar cord circuits, to a trunk lino going to any desired exchange, two of these outgoing trunk lines The one terininating in jack J" extends to a manual errcl'iange while the one terminating in the jack 5? extends to an automatic exchange.

Having briefly described the apparatus shown in the drawings, a detailed description of its operation will now be given. For this purpose, it will be assumed that the subscrioer at substation A desires to obtain a connection with the subscriber in the distant automatic exchange. In order to oh:

tain this connection, the subscriber at substation A must call the operator at the position shown in Fig. 2, and he will therefore remove his receiver and operate his calling device in accordance with the number of the operator, which we will assume is the number 01. Vr hen the receiver is removed at substation A a circuit is completed over the two line conductors 11 and 12 in series for the line windirg 16 ot' the relay 18. The line winding 16, upon energizing, partially attracts the armatures 25 and 28. That is, the armature engages its working contact but it does not break the springs 31, while the armature 28 engages its working contact but it does not break the springs 29. its a result of the operation ot the line winding 16, a circuit is completed at armature 538, for the switching winding ot the relay 18 in series with the motor magnet 17, while at armature the test wiper 4a) is connected to the above circuit at a point mid way between the switchii'ig winding and the motor magnet. The operation ot the line switch C now depends upon whether or not the trunk line with which the s itch wipers 346, inclusive, are in engagen'ient is busy. It the trunk line is busy, there will be a ground potential present upon the test contact engaged by the test wiper s5, the switching winding 15 will be short circuited, and the motor magnet 17, being supplied with direct ground by way of the said test wiper, will operate to advance the switch wipers step by step in search ot an idle trunk line. However, it will be assumed in the present case that the trunk line with which the switch wipers 48- 16, inclusive, is associated when the receiver is ren'ioved at substation A idle. It will be assumed further that this trunk line is the one shown in the drawings extending to the selector E and terminating in bank contacts lT SO, inclusive. Under these conditions, immediately 'tollowing the cuergization ot the line winding 16. the switching winding 15 will be energized in series with the motor magnet 17. Upon energizing, the switching winding attracts the armatures 23 and therely extending the line ot the calling substation by way (it wipers 4:3 and 46, bank contacts 17 and 5t), armatures 112 and 117 and their back contacts, to the upper and lower windings of the line relay ot the selector F.

The line relay T5 of the selector E is energized over two sides of the calling line in series and, upon operating, completes the circuit of the slow acting relay 76. The latter relay, upon energizing, prepares the operating circuits of the selector E at ar mature 93 and at arn'iature 92 places ground upon the release trunk conductor thereby establishing a holding circuit for line switch C. which may be traced "from ground on release trunk conductor 94-, bank contact test wiper l5, armature and its working contacts, which includes the spring 26, switchingwinding 15 of the relay 18, and thence through the winding'ot the motor magnet 17 to battery. A branch of this holding circuit also extends by way of the priyate normal conductor ll) to niultipled test contacts in the banks of connector switches which have access to the line of the substation A whereby the said line is pro tected from intrusion in the usual manner.

At this point it will be well to explain the operation of the line switch C a little more in detail. It will be uneerstood that, when the switching winding 15 energized, it attracted the armatures 22-3, jet and 3t), and besides this completely attracted the armatures 25 and it being, of course, assisted in this operation by the line winding 16, which, though its circuit is opened a armatures 23 and 30, is slow acting and thus assists the switching winding in attracting the armaturcs. The switching wini'ling 15, it will be seen, is in a different magnet circuit than is the line winding 16, on account oi the soft iron shield. 11). loweyer, he switching winding adapted once the armaturos have been comp etely a tracted, to hold them in this posit-ion, this being accomplished by so constructing the shield 19 that it does not comp etely separate the n'iagnetic circuits oi the windings 5 and 1? In order to provide "tor proper operation of the line switch, armatures 2 and are adjusted to engage their working contacts a short interval before the springs 29 operated by armature 28 break This provision made so that the r of the switching winding 15 will not be opened until the above traced holding cir cuit has been estr-iblished.

The calling subscriber at substation A may now operate his calling device in accordance with the first digit 0 of: the desired operator's number. By this operation ten interruptions are produced in the circuit ot the line relay 7;) which retracts its armature a corresponding number of times in response thereto, each than, sending an impulse of current over the follow circuit: from ground, by way of back contact and armature 11o, armature ill) and its back contact, armature J3 and its front contact, oil normal springs 95 and 96, winding of the slow acting relay 77, and hence through the ring of the vertical magnet (3 to bat- The aboye is the circuit over which the first impulse to the vertical magnet is sent. Upon the first yertical step of the shaft, the ct? normal springs are shifted and the remaining impulses to the vertical magtraverse a different circuit, which is the net same as the one previously traced except that it includes the oil normal springs 95 and 9?. and armature 101 and its front contact, relay 77 being new in an operated. po-

lU-ll sitiou. The vertical magnet 83 operates to raise the switch wipers 130 133, inclusive, step by stop until they are placed opposite the tenth level of hank contacts. The slow acting relay '77 is ener 'ized in series. with the verticalv magnet and maintains its arnnu ture anti-awed tlu'oughout the vertical more ment of the switch. Upon the first vertical step of the shaft, the cit normal spring 106 is operatml and a, circuit. may now he traced extending fronr ground on release trunk conductor 94;, by way of spring 123 audits resting Contact, armature 100 and its front contact, elf normal spring; 106 and its working contact and through the winding: of the stepping relay 78 to battery. Relay 78 upon energizing, prepares the circuit of the rotary magnet 84: at its armature 103, and at its armature 108 establishes a locking for it ill; which extends from ground, by way oi armature i108 and its front (01ll'.&l(ft, armature 1'10 and its hack contact, armature Ill and its back contact, front cmiturt and armature 91, oil normal spring M6 and its working contact, and thence thrmigh the winding of relay 78 to battery. It will be noted that the slow acting relay 77., upon attracting; its armature, completed a circuit in multiple with the one of the stepping; relay 78 which extends from ground on release'trunl: conductor 9% by ray of spring; 123 and its resting contact,

armature lOOhnd its working contact resistai'ice 105, armature 1% and its back eontact, (trough the winding-of the rotary magnet to battery. The above circuit is completed only :t'or a short interval, that is, until the re ay 78 is energized, and as it includes the resistance the rotary magnet 8-f-l: operated. The spring; 107 is adapted to be brought into engagement with its -working contact by the switch shaft when it is brought opposite thetenth'level of bank contacts. This may be acco1n plisl'ied by any suitable cam arrangement. hen the spring 10'? engages its worlci contact a circuit is completed extending; from ground on release trunk conductor 94:, by way of srnring 12 and its resting; contact, armature 100 and its front contact, spring: 1.07 and its working; contact, and through the winding-of slow acting relay 79 to battery. Slow acting relay 79 is energized over this circuit andQupon opeiiating opens the previously traced locking circuit of the stepping: relay 7S and causes this relay to deenergize thereby opening; a point in the circuit oi the rotary magnet. Shortly after the. termination of the vertical movement of the switch, the slow acting relay 7'? is deenergized and retracts its armature 100, but as the relay 78 is now deenergized, no circuitis completed for the rotary magnet 84L.

The calling subscriber at substation A may now operate his calling device S in accordance with the next and final digit 1 of the ooerators number. By this operation one terruption is produced in the circuit of the line relay and an. impulse of current sent over a. circuit extending; from ound, by my otbac.- cent: and arnni. ture l'li") armature and its heel; eontznl armature )3 and it; Front contact, oi? normal sprin and 9'7, armature 101 and its baclr contach and thence through the windot the rotary mug-n t to batterv.

The rotary magnet 8%- operetes to rotate the switch. wipers 130-138, inclusive, into cngrageinent with the first set of ha contacts the tenth level. The slow acting relay 79 energized in multiple with. the rotary inee'net and operates ts ernniluire 1110 to g open the ""HMECtlOH of the test wiper 13:32 'wi t hi the eppiug relay 78. H 1 1.1L. runner OLQI'RMUD or the selector l-u "pends upon whether the truu line with th the r-uritcli wipers are now in engage meet is busy or not. issuinii the trunk line to be busy iher-e will he a i lied present upon the test co by the to t wiper 1'32. Then dcener oration oi the slow ing relay 79. circuit inoing i'ron'i said he traced exten grounded test contact, by way of the test wiper 132, armature 115 and its hack con tact. arinaturev 110- and its hack contact. armature ill and ts back contact from contact and miniature 91 oii' normal spring 106 and its working contact. and thence. through the winding of the stepping relay 78 to hattery. The stepping relay 78 is en: ergized over this circuit and, upon operating. establishes a locking; circuit for itsell at its armature 108 and at its armature 103 comengagement with the last trunk line of the group extci'iding to the desired operatofis position. The trunk lines in the tenth levelv ere divided into grou s by means of? a can'i arrangement such as 12%. The cam 124 has certain projections on it such) as 125, 126, and 127 which are adapted to operate the springs 122 and 123 when the switch wipers are rota-ted into engagement with the last trunk line in each group on the tenth level. The projections on the ram 124; are so constructed that the switch wipers may he readily rotated into engage meet with any runl: line in any group and released without any interference in their restoration to normal. It will be seen that by the operation of the springs 122 and 123 the release trunk ground is removed from armature 100 of the slow acting relay 7? so that the operation oi the relay 78 will not cause the operation of the rotary magnet 84: and therefore no further rotation of the switch vill occur. -A.S the switch wipers 130133. inclusive. are in engagement witha busy trunl line the switching' relay will not he energized. A circuit may now be traced extendine from the busy tone machine T. conductor 129, spring and its work ngcontact. "l'roi'it contact and armature 102. back contact and arn'iature 109, armature 113 and its back contact, to the upper heavy tllliill conductor. This tone is audibleto the subscriber at substation A and he will know that all trunk lines extending to the desired operators position are busy and he will therefore replace his receiver upon the switchhook thereby initiatingthe release of the operated switches in the usual manner.

it will now be assumed that the switch wipers 130133, inclusive, are rotated into engagement with an idle trunk line eKtending; to the desired operators position, and it will. be assumed further that the selected trunk line is the one terminating in bank contacts 134F137, inclusive. lVhen the switch wipers are rotated into engagement with this trunk line there will be no ground potential present upon the test contact 136 engagged by the test wiper 132 and there will be no circuit completed tor the stepping relay 78. The switchingrel ay 80. being no longer short circuited. inu'nediately energizes in series with the said stepping relay. As a result of the en-crgization of relay 80, the line of the said substation A is disconnected from the windings of the line relay 7 and is extended by way of armatures 112 and 117, wipers 130 and 133., bank con tacts 13 i and 137, trunk conductors 140 and 142. through the winding of relay 200 and through the winding of relay 201, to around and battery. respectively. The relay 201i is of such low resistance that it is not energized in series with the high resistance relay 201 though the latter relay is up crated. Relay 201. upon energizing, at its armature 206 completes the circuit ot the line lamp L whereby the trunking operator is notified that a connection is desired with one of the outgoing trunk lines. It will be noted that. low resistance relay 81 in the selector E is included in the energizing circuit of the relay 201. This relay is operated and serves to maintain the slow acting- .rehrv 76 energized so as to prevent the release ot the selector E. It will be seen that by the provision of relay 81 only a three conductor trunk is necessary between the trunking; operators position and the first selectors, the release trunk conductor not being extended to the position. a The trunking operator, upon perceiving the lighted condition or the line lamp L, will insert the answering plug of an idle cord circuit into the jack J which, we will assume, is the plug P of the cord circuit 0. hen the plug P is inserted into the jack 5, the relay 213 is energized in series with the cut oil relay 200. The latter relay is energized over this circuit and operates at its armature 205 to open the circuit of the line relay 201. Relay 201, upon deenerg'izin'g, extinguishcs line lamp L. Relay 213, upon energizing, closes the circuit ot the supervisory lamp L at armature- 228 but this lamp is not lighted at this time as the supervisory control relay 21% is energized over the calling); subscribers line loop. Another circuit completed when the plug P is inserted into the jack J nay be traced from ground at. the calling sultiscribefis line switch, by way of the bus-bar 33, conductor 39, front contactand armature 2t, wiper 4 1, bank contact 48, front contact and armature 11%, wiper 131, bank contact- 135, conductor 141, sleeve of the jack J, sleeve ot the plug; 1 tiroug'h the winding of the relay 210 tothe junction point 217. where the circuit divides, one pate extending through the winding of relay 211 to battery the other extending through the winding of relay 212 to battery. As there is direct ground on the discriminating trunk conductor M1 all the relays 210, 211 and 212 will be energized. A circuit may now be traced extending trom ground by way of armature 223 and its front Contact, front contact and ar mature 221, and thence through the lamp L to battery. Another circuit may be traced from e-round by way of "front contact and armature 225, through the lamp L to battery. The lamps L and L are of ditlerent colors and, as both are operated, serve to inform the trunking operator that the calling subscriber is entitled to unrestricted service. It only the lamp L were lighted, as would. be the case were only the relays 210 and 211 energized over the discriminatinn trunk. the operator would know that the calling subscriber would be entitled only to service over the trunk lines going to the manual exchange, such as the trunk line terminating in the jack J. it the lamp L was the one operated, as; would be the case it only the relay-2lO was energized, the operator would know that the calling subscriber would only be entitled to connections over the trunk lines extending to the automatic exchange such as the trunk line terminating in the jack J Upon perceiving the class of service which the calling subscriber is entitled to, the operator will actuate her listening key K theretit) eashes by associating her head set with the cord circuit in order to ascertain what exchange the calling subscriber desires. Assuming that the calling party desires a connection with a subscriber in the manual exchange the operator will test the various trunk lines extending thereto by means of the tip of the plug P in the usual mam anth upon finding an idle trunk line. insert the plug P into its associated jack. ill will be assruned that the trunk line terminating in jaeh J is the one selected for use by the operator. l hen the plug l? is inserted into the jack J, the relay 216 energized over the sleeve oi the jack This relay upon operating; at its arn'iature completes the circuit of the supervisory lamp L The operator will now actuate her ringing key in order to operate the ringdown signal bridged aorossthe trunk at the manual eX- change. he trunk lines extending to the manual exchange may terminate there in the usual. equipment the only special provisionbeing that the operator at the manual exchange, upon answering, will place batlery upon the trunk line in such a direction as to operate the clectropolarized relay 215 in the cord circuit in order to inform the operator at the private branch exijzl'iange of her response. The subsequel'it operations by which a connection is extended to the der'iired called line in the manual exchange will take place in a well known manner andneed not be described herein. i

It will now he assuniied that the calling -:-uibscriber at substation A desires a connection with a subscriber in the automatic exchange. After ascertaining this 351101; the tlllllhlilg operator will insert the plug P into the jack of the first idle trunk line extending to this enchange, which we will By this operation assume the jack o the relay 216 is energized as before, and the supervisory lamp L is lit. The oper alor will now throw her calling device key K thereby placing the impulse springs of the calling device S in bridge oi the conductors oi the outgoing trl'lnk line, and operate the calling device S for the digits of the called subscribefis number, after which she will restore the key K to normal. The connection to the subscriber in the automatic exchange will be completed in the well known manner and the subscril'ier automatically signalled. W hen the called party answers battery is reversed over the out goi 4,; trunk line and the electropolarized rela' 215 in the cord circuit U operated to extinguish the supervisory lamp l4. By the eli'acement of this signal the operator in the private auton'iat-icexchange is notified of the response of the called party.

When the conversation is terminated, both subscribers will replace theirreceivers upon the switchhook. When the receiver is re "resistance R connected to it.

placed at substation A the circuit of the re lay 21a in the cord circuit 0 is opened and this relay deenergizes to complete the circuit oi the supervisory lamp L. Another result of the replacement of the reoeiverat substation it is that the circuit or relay 81 in the selector E is opened. This relay then deencrgizes opening the circuit of the slow acting relay 76. Upon the deenergization of the latter relay, the holding circuit 01' the switch ing relaybt) and the switching winding of the line switch C is opened and these relays then deenergize. Relay 80, upon deenergizing, completes the circuitof the release magnet 82 oi the selector E whereby the switch is restored to normal position. It will be noted that during the release of the selector E, test wiper is not connected to the stepping relay 78 as the slow acting relay '76 is now deenergized. This provision is made so that should the Wipers ol' the selector E engage any busy trunk lines during this restoration to normal the stepping relay 78 will not be energized to interfere with the release of theselector. In the line switch G, the switching winding 15, upon deenergizing allows all its armatures to restore to normal. ln this manner the release of the connection takes place.

When the receiver is replaced at the called substation in the distant automatic exchange the normal battery flow over the incoming trunk line is restored to normal and the polarized relay in the cord circuit- 0 is deenergized to light the supervisory lamp L By the operation of the supervisory signals L and L the operator is informed of the disconnection and she will withdraw the plugs of the cord circuit from the associated 'ack. When the nin P is withdrawn from J l a the jack J, the bridge, across the conductors oi the outgoing trunk line is broken and the automatic switches in the distant exchange are released. When the plug P is Withdrawn from the jack J the cut oil relay 200 in the trunk circuit is deenergized and the connection is thusreleased.

From the foregoing it will be apparent as to how the subscribers in the private automatic exchange are divided into diliorent groups according to the class of service to which they are entitled. Thatis, a subscriber that is entitled to unrestricted service has his discriminating trunk conductor, such as 39 connected to the busbar 33, which has direct ground upon it. A subscriber entitled only to connections to the manual exchange has his conductor similar to 39 connected to the bus bar 34 which has groundthrough the In this case, when a connection is extended through to the trunking operators position and is answered by means oil a cord circuit such as 0, only the relays 210 and 211 are energized, the relay 212 being marginal and not receiving suflicient current to energize it in series with theresistance R. Only the lamp L is operated and the operator is thereby informed the class of service which the calling subscriber is entitled to. Should the calling subscriber only be entitled to extend connections over the trunk lines going to the automatic exchange the conductor similar to conductor 39 will be connected to the bus-bar 35 which has ground through the resistancelt. This resistance is somewhat higher than the resistance R- and only allows enough current to flow over the discriminating trunk to energize the relay similar to relay 210, the relays 211 and 212 remaining in an inoperative position. Thus the lamp L is the only one operated and in this manner the operator is informed that the calling subscriber is entitled only to connections over the trunk lines extending to the autoi'natic exchange. The subscribers who are not entitled to any outside connections at all have their conductor, such as 39, connected to the bus-bar 36 which is ungrounded. Should one of these subscribers attempt to obtain a connection on one of the outgoing trunk lines, a line lamp, such as L, at the operators position would be lighted and the operator would answer in the usual manner by means of a cord circuit, such as 0. As there is no ground present upon the discriminating trunk conductor neither of the relays 210, 211 or 212 is energized though the supervisory control relay 21 i will be energized over the calling subscribers line loop. A distinctive tone is now given to the calling subscriber over a circuit extending from the tone machine T by way of front contact and armature 231, back contact and armature 220, ring of the plug P, and thence to the lower talking conductor of the associated trunk circuit. This tone will serve to inform the calling subscriber that he is not entitled to any service whatsoever over the outgoing trunk lines. As neither of the lamps L or L is lighted the operator will know that the subscriber calling is not entitled to outgoing service and she will not operate her listening key in order to answer the call. When the calling subscriber hangs up the relay 214: will be deenergized and the lamp L lighted. This signal will serve to inform the operator that the calling subscriber has replaced his receiver and she will withdraw the plug of the cord circuit 0 from its associated jack.

At this point it is convenient to briefly de scribe the operation of the line switch C when the line of the substation A is called. Immediately upon the connector engaging the bank contacts associated with the line of the substation A, ground is placed upon the private normal conductor 40 by way 01? the test or private wiper of the connector. This closes a circuit through the switching winding 15 of the relay 18 and thence through the winding of the motor magnet 1? to battery. The winding 15 is energized over this circuit but only partially attracts the armatures 23 and 30, that is enough to disconnect the line of the substation A. from its normal battery and ground connections in the line switch C. On account of the soft iron shield 19 it has no operative ei'l'ect on the other armatures. he ari'natures 23 and 30 are prevented from being completely attracted by a mechanical interlocking device cont-rolled by the armature or the line winding 16 oi the relay 18. V

In order to describe the operation of the selector E when it is used in an ordinary connection, it will. be assumed that the subscriber at substation A desires to obtain a connection with a local subscriber in the private automatic exchange. in order to do this he will remove his receiver and operate his calling device in accordance with the digits ot the desired subscribers number. When the receiver is removed at substation ii, the line switch 0 operates, as before described, to extend the calling line to an idle first selector switch which, we will assume, is the selector E.

Immediately upon the calling line being extended to the selector E, the line relay is energized over two sides ot the calling line in series and operates to close the cirunit of the slow acting. release relay T6. The latter relay operates in the usual manner to prepare the operating circuits of the selector and to establish a holding circuit for the line switch C.

The calling subscriber may now operate his calling device in accordance with the first digit of his desired number. By this operation a series of interruptions is produced in the circuit of the line relay 75 which retracts its armature a plurality of times in response thereto. At each retraction of armature 90, an impulse of current is sent to the vertical magnet 83 in series witlrthe slow acting relay 77. The vertical magnet operates in the usual manner to raise the switch wipers 130%38. inclusive, step by step until they are placed opposite the level of bank contacts which is allocated to trunk lines extending to tnc desired group 01 connector switches which have access to the line of the called substation. The slow acting relay 7, is energized in series with the vertical magnet and. upon the first oil normal step of the switch, completes a circuit for the stepping relay 78. The latter relay upon energizing, establishes a locking circuit for itself at its armature 10S and atits armature 103 prepares the rotary magnet circuit. Atthe termination of the vertical movement of the switch, the slow acting relay 77 deenergizes and completes the circuit of the rotary magnet 8d. The rotary magnet 8st operates to rotate the switch Tltlta'i into groups, an opt wipers into engagement with the first set of bank contacts in the selected level and at its armature 111 breaks the locking circuit of the stepping relay 78. The latter reay deenergizes opening the circuit of the rotary inagnet which deenergizes also.

It the trunk line with which the switch wipers are now associated is busy there will be a ground potential present upon the test contactengaged by the test wiper 182 and the stepping relay will be again energizer.

Relay 78 operates in the usual manner to establish a locking cicuit for itself and to complete the rotary magnet circuit. Rotary magnet Se operates to rotate the switch wipers into engagement with the next trunk .line in the selected level and to break the locking circuit oi the stepping relay \Cdlt'li deenergizes opening the circuit of the rtary magnet which deenergizes also. The alternate operation of the stepping relay and the rotary magnet 84; will continue until an idle trunk is found. Vihen this occurs there will be no ground potential present upon the test contact engaged by the test .wiper 132, the switching relay 80, being no longer short circuited, will be energized in series with the steppingrelay 78. Relay 80, upon energizing, extends the line of the walling subscriber to the line relay of the selected connector switch.

The subsequent operations by which the connection is finally completed and the called sub..criber signalled will take place in the usual. manner. hen the conversation is terminated the operated switches will be released upon the subscriber at the calling substation ii replacing his receiver upon the switchhool: in the same manner as was described hereinbetore.

Having fully described and ascertained the features of the invention, what is con sidered to be new and desired to have protected by Letters latent will he pointed out in the appended claims.

Wl at l clansv is:

l. in a telephone systen i, calling line, dirators position, a trunk line terminating in a jack at the said positioin suliscriber-controlled means for autoinati'nlly connecting one oi said call- 11;;- lines widi said trunlrline, called lines, a cord circuit i'or exending the connected trunk line il the direction oi" i one oi said i. 11 1 17 m .1 s n; m

in to. ,nes, core cncuii icin coininon to said trunk line and othe' similar trunk lines, and means in said COtl circuit indeover the calling line for connecting one of said calling lines withv said trunl; line, other trunk lines terminating at said position leading to different exchanges, a cord circuit for connecting the first mentioned trunk line to one of said other trunk lines, means for noti tying the operator at said position if the calling subscriber is entitled to he connected to any one oi? said other trunk lines, and he in said, cord circuit responsive to its connection with said trunk line or selec' tively operating said notifying means.

3. in a telephone system, calling lines, an operators position, a uni: line terminating in a jac r at said position, means for connectone of said calling lines with said trunk line, othe nating .1 unit he ,1:

position leading; to

cord circuit for connecti turned trun line tonne oi said 0th ink lines, luears for in said lines dr llerniarl; ently, and relays in said cord circuit responsive to t :e connecti n of said c" l circuit '\'-:ith said first mentioned trunk line and operated from i markingineans for notifying the operator at said position it the calling subscriber is entitled to be connected to certain of said other trunk lines.

4. in. a telephone system, calling lines dividcd into groups, an operators position, trunl-t lines terminating 1n jacks at said position, other lines, a cord circuit or extending co: nections from said trunk lines to s. id other lines, means for connecting a calling line in one group with one of said trunk lines, means in said cord circuit responsive to its connection with the connected trunk and operative over a circuit closed by nea-ns individual to the calling line for givv the ope 'ator at said position a signal, means for connecting a calling line in another group .with another of said trunk lines, and means in said cord circuit I'QSDOH- si co to connection with the said other connected trui'ik line for giving the operator :1

ignal.

different p,

.ln a telephone systei calling lii'ies, trunk lines, an operatofis osition, a cord circui at said position for connecting one oi said calling lines with an idle one 0t said trunk lines, a pair of relays individual to said cord circuit, one of said relays energized when connection is made with one of said calling; lines, both of said relays energized simultaneously when connection is made witl another of said calling lines, and means controlled by each of sai relays for giving a different signal to the operator at the said position the signal given depending on the line with which. the connection. is made.

(i. In a telephone systen1,'call.ing lines divided into groups, trunk lines, an operators position, an automatic switch for extending said calling lines to said position, a double plug cord clrcuit at sald position for conat said.

nectingone of said calling lines with one of said trunlr lines, a pair of rel ys in said cord circuit, one of said relays energized when connection is made with a calling line of one group, the other of said relays energized when connection is made with a call ing line of another group. and means controlled by said relays for giving a signal of one kind to the operator in said first connection and a dili'erent signal in said second connection. 7

7. in a telephone system, calling lines divided into classes, trunlr lines, an operatofis position, means including an automatic switch i'or extending said calling lines to said position, a cord circuit at said position for connecting one of said calli lines with one of said trunk lines, relays in the said cord circuit one less in number than the number of cla ses oi calling lines, class naling circuits controlled by said relays. means tor operating varying numbers of said relays when coi'inect'ton is made with the calling lines ol ditlerent class I, and a circuit tor said relays extending through said switch.

8. in a telephone system, calling lines diyided into classes, trunk lines, an operators position, a cord circuit at said position tor connecting one of said. calling lines with one of said trunk lines, a relay in said cord circuit energized when connection made with the calling line of one class, another relay in said cord circuit energized when connection made with a calling line of another class, said first relay remaining inoperative in the second connection to prepare a circuit which controlled by said second relay for placing a distinctive tone on said calling line.

9. in a telephone system, calling lines divided into classes, trunk lines, an operators position, a cord circi'lit at said position for connecting one of said calling lines with one of said .trunk lines, a relay in said cord circuit eiiergized when connection is made with a ailing line in one class, and iii-cans controlled by said relay for placinga tone on the calling line.

it). In a telephone system, subscribers lines of dil'l'u'cnt classes, an operatofis switchboard, a trunk line, automatic switching mechanism controlled over a calling one o't said lines to extend such line to said switchboard via said trunk line, manual equipment for answering the call, and visual signalling apparatus controlled solely over said trunk line and automatically responsive to the answering of the call for notifying the operator oi the class to which the calling line belongs.

11. In a telephone system, subscribers lines of different classes, an operators switchboard, automatic switching mechanism controlled over a calling one of said lines to extend such line to said switchboard, a cord circuit adapted to be connected with said line at said switchboard to answer the call, a plug and a jack by means of which the connection is effected, and visual signalling apparatus automatically responsive to the insertion of the plug in the jack tor'noti'tying the operator of the class to which the calling line belongs.

12. In a telephone system, subscribers lines different classes, an operators switchof board, automatic switching mechanism controlled over a calling one of said lines to extend such line to said switchboard, a s1gnailing circuit including a conductor indiridual to the calling line and a conductor connnon to said lines, the resistance of said circuit depending on the class of the calling line, and risual signalling apparatus selectively controlled over said circuit in accordance with the resistance thereof to notify the operator of the class to which the calling" line belongs.

13. In a telephone system, subscribers lines of different classes, an operators switchboard, automatic switch mechanism tor extending said lines to said switchboard when calling, a signalling circuit established when a line is so extended, meanstor establishing a predetermined steady flow of current in said circuit, the value of the current flow depending on the class to which the calling line belongs, and class signalling apparatus selectively controlled over said circuit in accordance with the value of the current flowing therein.

14:. In a telephone system, subscribers lines ot dil'l'erent classes, an operators switchboard, automatic switching mechanism for extending said lines to said switchboard when calling, resistances of different values, one for each class, a signalling circuit estal lishcd when any one of said lines is extended to said switchboard, such circuitincluding the particular resistance which corresponds to the class to which the calling line belongs, and class signalling apparatus controlled over said circuit.

In witness whereof, I hereunto subscribe my name this 17th day of May, D. 1921.

JOHN E. GARDNER. 

